title: Orally fed seeds producing designer IgAs protect weaned piglets against enterotoxigenic Escherichia coli infection.
abstract: Oral feed-based passive immunization can be a promising strategy to prolong maternal lactogenic immunity against postweaning infections. Enterotoxigenic Escherichia coli (ETEC)-caused postweaning diarrhea in piglets is one such infection that may be prevented by oral passive immunization and might avert recurrent economic losses to the pig farming industry. As a proof of principle, we designed anti-ETEC antibodies by fusing variable domains of llama heavy chain-only antibodies (VHHs) against ETEC to the Fc part of a porcine immunoglobulin (IgG or IgA) and expressed them in Arabidopsis thaliana seeds. In this way, four VHH-IgG and four VHH-IgA antibodies were produced to levels of about 3% and 0.2% of seed weight, respectively. Cotransformation of VHH-IgA with the porcine joining chain and secretory component led to the production of light-chain devoid, assembled multivalent dimeric, and secretory IgA-like antibodies. In vitro analysis of all of the antibody-producing seed extracts showed inhibition of bacterial binding to porcine gut villous enterocytes. However, in the piglet feed-challenge experiment, only the piglets receiving feed containing the VHH-IgA-based antibodies (dose 20 mg/d per pig) were protected. Piglets receiving the VHH-IgA-based antibodies in the feed showed a progressive decline in shedding of bacteria, significantly lower immune responses corroborating reduced exposure to the ETEC pathogen, and a significantly higher weight gain compared with the piglets receiving VHH-IgG producing (dose 80 mg/d per pig) or wild-type seeds. These results stress the importance of the antibody format in oral passive immunization and encourage future expression of these antibodies in crop seeds.
authors.affiliation: Department of Plant Systems Biology, Vlaams Instituut voor Biotechnologie, 9052 Ghent, Belgium. vikram.virdi@psb.vib-ugent.be
authors.forename: Vikram
authors.initials: V
authors.lastname: Virdi
authors.forename: Annelies
authors.initials: A
authors.lastname: Coddens
authors.forename: Sylvie
authors.initials: S
authors.lastname: De Buck
authors.forename: Sam
authors.initials: S
authors.lastname: Millet
authors.forename: Bruno Maria
authors.initials: BM
authors.lastname: Goddeeris
authors.forename: Eric
authors.initials: E
authors.lastname: Cox
authors.forename: Henri
authors.initials: H
authors.lastname: De Greve
authors.forename: Ann
authors.initials: A
authors.lastname: Depicker
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial / Q000378:metabolism; D017360:Arabidopsis; D001483:Base Sequence; D020895:Enterocytes / Q000382:microbiology; D054307:Enterotoxigenic Escherichia coli; D004927:Escherichia coli Infections / Q000517:prevention & control / Q000662:veterinary*; D007116:Immunization, Passive / Q000662:veterinary*; D007070:Immunoglobulin A / Q000737:chemistry / Q000378:metabolism; D007074:Immunoglobulin G / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D012639:Seeds / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology* / Q000517:prevention & control*
chemical_list: D000907:Antibodies, Bacterial; D007070:Immunoglobulin A; D007074:Immunoglobulin G
keywords: antibiotic replacement; enteric infections; molecular farming; mucosal immunity; nanobody